Objectives

Mass shootings seemingly lie outside the grasp of explanation and prediction, because they are statistical outliers—in terms of their frequency and severity—within the broader context of crime and violence. Innovative scholarship has developed procedures to estimate the future likelihood of rare catastrophic events such as earthquakes that exceed 7.0 on the Richter scale or terrorist attacks that are similar in magnitude to 9/11.

Methods

Because the frequency and severity of mass public shootings follow a distribution resembling these previously studied rare catastrophic event classes, we utilized similar procedures to forecast the future severity of these incidents within the United States.

Results

Using a dataset containing 156 mass public shootings that took place in the U.S. between 1976 and 2018, we forecast the future probability of attacks reaching each of a variety of severity levels in terms of the number of gunfire victims killed and wounded across three different choices of tail model, three different scenarios for future incident rates, and other parameters. Using a set of mid-range parameters, we find that the probability of an event as deadly as the 2017 massacre in Las Vegas occurring before 2040 is 35% (90% uncertainty interval [8, 72]) and we characterize how this projection varies substantially with choice of modeling parameters.

Conclusions

Our results suggest an uncertain, but concerning, future risk of large-scale mass public shootings, while also illustrating how such forecasts depend on assumptions made about the tail location and other details of the severity distribution model.

中文翻译：

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预测美国大规模枪击事件的严重性

目标

大规模枪击似乎超出了解释和预测的范围，因为在犯罪和暴力的更广泛范围内，就频率和严重程度而言，它们是统计上的异常值。创新奖学金已开发出程序来估算未来罕见灾难事件的可能性，例如里氏地震超过7.0级或恐怖袭击的程度与9/11类似。

方法

由于大规模公共枪击事件的频率和严重性遵循类似于这些先前研究的罕见灾难事件类别的分布，因此我们使用类似的程序来预测美国境内这些事件的未来严重性。

结果

使用包含1976年至2018年间在美国发生的156次大规模枪击事件的数据集，我们根据三种不同选择造成的枪伤和伤亡人数预测了袭击达到各种严重程度的可能性尾模型，未来事件发生率的三种不同情况以及其他参数。使用一组中程参数，我们发现2040年之前发生的与2017年拉斯维加斯大屠杀一样致命的事件的概率为35％（不确定性区间为90％[8，72]），并且我们表征了这种预测如何变化基本上与建模参数的选择有关。

结论

我们的结果表明，大规模大众枪击事件的未来风险不确定，但与此有关，同时也说明了这种预测如何取决于对尾巴位置和严重性分布模型其他细节的假设。